Reloaders Corner: Case Trimming: finishing the job

Facebooktwittergoogle_plusredditpinterestlinkedintumblrmail
Facebooktwittergoogle_pluspinterestyoutube

So you have a sack full of trimmed cases. Now what? Here’s what! A few tips on final preparation that may even promote better accuracy. Keep reading…


Glen Zediker


The most basic and necessary tool or tools we’ll need to get the freshly-trimmed case into shape to take on a new bullet is an “outside” and “inside” chamerfing appliance. These are most popularly housed in one hand-held tool: one end does the outside and the other does the inside. Of course (of course) there are options, and some are right dandy.

LE Wilson chamfer tool
Here’s a basic and common LE Wilson inside/outside chamfering too. One end does the outside, the other does the inside. Shown is a 45-degree tool.

After trimming the case mouths will be square, flat, and appear wider-walled than before. That’s normal.

There will usually be a little edge-ring of brass on the exterior surface of the case neck, and that’s the reason for the wider appearance. That’s easily remedied. It takes only a light skiff using the “outside” function of the tool.

trimming burr
That little ring of brass around the top outside edge of the case neck: just get it gone. Doesn’t require a cut, just a skiff with an outside deburring tool.

Don’t cut into the outside, just remove the ring. No bevel is necessary; that only thins the case mouth. If the ring is left standing, the case might not want to feed, and then there will be little shards of brass here and there.

Next, the inside. The inside edge of the case mouth needs to be broken and also beveled to more easily accept a bullet. Now we’ve got options in depth of the bevel and angle of the bevel.

The long-time “standard” is a 45-degree chamfer. That functions okay to allow most bullets to sit unsupported in the case neck prior to seating. I believe, and I’m not nearly alone, that a steeper angle is better. For anyone loading bullets that are of a longer, “spikier” form, I strongly recommend something closer to 30 degrees, or less. These are often called “VLD” cutters or chamfer tools, and that is because these tools followed the “low-drag” style bullets that, among other attributes, featured relatively longer, more steeply angled boat-tails. They also have relatively thinner jackets (“J4”). Essentially, a 45-degree pathway and the geometry on the bullet didn’t mate up.

Lyman VLD chamfer tool
Here’s a Lyman “VLD” chamfer tool. It’s got a 22-degree angle. I’ve used other brands that were 19 and 20, and I honestly don’t know that a couple degrees makes much difference. However! There’s a world of difference between this and a 45-degree tool.

The result of a greater angle mismatch is that the bullet gets a pretty hard start into the case neck, and it can also get a crooked start, and that’s because it’s not sitting “into” the neck very far. It’s in a precarious position and easily tilted. These long bullets create what amounts to more leverage in less-than-perfect case necks, which is going to be the most of our case necks unless we’re neck turning. (It’s also why I’m a big believer in a bullet-seating stem that engages farther down the bullet nosecone; this also helps reduce the angular deflection in seating.) I’ve seated and then pulled bullets from cases with 45- and 20-degree chamfers, for instance, and those from the shallower angle show noticeably less scuffing. (Plus, many of the custom-made low-drags feature a “pressure ring,” which is a tiny elevated ring right at the boat-tail/shank junction, usually about 0.0005 diameter, which helps obturation. That ring can get deformed by a 45-degree chamfer.)

It’s not the depth into the case neck cylinder that improves the transition into the case neck, so a “bigger” cut with a 45 won’t do a thing. A steeper cutter is going to make a deeper extension into the case neck simply because the angle is steeper.

Cutting the inside, do not go for a knife edge! For a yardstick, I suggest going about halfway on a 45-degree cut and 2/3 on a VLD-style chamfer tool. By that I mean that the appearance of the wall thickness at the case mouth is roughly half after chamfering that it was before.

Forster 3-way trimming head
There are also “all-in-one” cutter/chamfer/deburr heads for some case trimmers. These are one bugger to set up, but they work well and save a ton of time and extra steps, and since it’s incorporated into the length-trimming operation, the chamfer consistency will be spot-on. Trick is finding one that cuts a shallower angle on the inside… If not, it’s going to produce better results overall to do this operation separately.

It is important, at least in logical thought, to have the same chamfer depth on each case to ensure perfectly consistent engagement with the bullet shank. Honestly, I don’t know if that shows up on a target, but it’s easily attained using either an LE Wilson or Forster case trimming base, as well as some others, with the addition of a chamfering tool in the apparatus to replace the length trim cutter. It’s an extra step in retooling and adjustment, but then if the cases are all the same length and the stops are set, each case mouth will have an identical chamfer.

LE Wilson neck reamer
Here’s a trick and half for seating flat-base bullets. These are difficult to get started straight since there’s no boat-tail to ease transition into the case neck. I use an LE Wilson inside neck reamer set to engage a feature built into that tool. LE Wilson added a short tapered area that can be run into a sized case neck, about 1/16 inch, that machines something close to a “shelf” that provides a nest for the flat bullet base. There’s a noticeable improvement in runout on the flat-base bullets I have seated with and without this cut. [Note: This is the “standard” inside neck reamer intended to remove excessive thickness in the case neck cylinder on fired cases, not sized cases; the feature just described is an accessory benefit and, again, is engineered for use on sized case necks.]

The preceding is a specially-adapted excerpt from Glen Zediker’s newest book Top-Grade Ammo. Available right’chere at Midsouth Shooters Supply. Visit ZedikerPublishing.com for more information on the book itself, as well as others.

Facebooktwittergoogle_plusredditpinterestlinkedintumblrmail

4 thoughts on “Reloaders Corner: Case Trimming: finishing the job”

  1. I have been waiting to see how other people respond to this article to temper my response and I can’t believe NO one has commented yet! I can’t agree with any of it. Actually, I do agree with one aspect and that is after trimming you DO have to de-burr/ chamfer the mouth of the brass but you do that as minimally as possible! By using that steep cutting chamfer tool you take way too much brass away making it too thin which causes a weaker grip on the bullet , which causes the neck to stretch, which causes trimming again, which causes pre-mature brass life, which causes etc., etc., etc., Let the die do it’s job and life will be normal again!!!

    1. The steeper/shallower chamfer reduces bullet jacket damage which is an asset to the performance of a long range round, especially. I’m not nearly as concerned with brass life as I am with my score. Take a 3500 dollar rifle and about that much more again in kit to a tournament halfway across the country, and an extra load or two on a case just doesn’t seem important. There’s way plenty of case neck “left” to retain a bullet. I usually do the “step ream” operation only once over the life of a case.

  2. Looking for a high volume low manual effort approach is the use of the vibratory tumbler that removes the lube to also remove the inner and outer rim created by the trim. This is best illustrated by the entertaining YouTube video “High Volume 223 On A Hornady LNL AP Progressive Press”. The video employs a RCBS lube die with a pricey Dillon trim/sizing die in one pass, thus not mucking up the case feeder and getting simultaneous shoulder and base references to match the trim length. Other methods reference only one datum. I find the approach works equally well on a Lee LoadMaster. Then to chamfer the cases, the video puts them in a Lyman vibratory tumbler to remove the lube and lets the media flow out so the cases are self chamfered. Very clean approach that works, and removes yet another one-at-a-time manual process.

Comments are closed.